High efficiency thermoelectric generation

ABSTRACT

A thermoelectric power generating system is provided that includes at least one thermoelectric assembly. The at least one thermoelectric assembly includes at least one first heat exchanger in thermal communication with at least a first portion of a first working fluid. The first portion of the first working fluid flows through the at least one thermoelectric assembly. The at least one thermoelectric assembly includes a plurality of thermoelectric elements in thermal communication with the at least one first heat exchanger. The at least one thermoelectric assembly further includes at least one second heat exchanger in thermal communication with the plurality of thermoelectric elements and with a second working fluid flowing through the at least one thermoelectric assembly. The second working fluid is cooler than the first working fluid. The thermoelectric power generating system further includes at least one heat exchanger portion configured to have at least some of the first portion of the first working fluid flow through the at least one heat exchanger portion after having flowed through the at least one thermoelectric assembly. The at least one heat exchanger portion is configured to recover heat from the at least some of the first portion of the first working fluid.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/954,786, filed on Jul. 30, 2013 and which claims the benefit of U.S.Provisional Appl. No. 61/678,511, filed Aug. 1, 2012 and U.S.Provisional Appl. No. 61/678,975, filed Aug. 2, 2012. The entirecontents of each of the applications identified above are incorporatedby reference herein and made a part of this specification.

BACKGROUND

1. Field

The present application relates generally to thermoelectric cooling,heating, and power generation systems.

2. Description of Related Art

Thermoelectric (TE) devices and systems can be operated in eitherheating/cooling or power generation modes. In the former, electriccurrent is passed through a TE device to pump the heat from the coldside to the hot side. In the latter, a heat flux driven by a temperaturegradient across a TE device is converted into electricity. In bothmodalities, the performance of the TE device is largely determined bythe figure of merit of the TE material and by the parasitic(dissipative) losses throughout the system. Working elements in the TEdevice are typically p-type and n-type semiconducting materials.

SUMMARY

In certain embodiments, a thermoelectric power generating system isprovided comprising at least one thermoelectric assembly. The at leastone thermoelectric assembly comprises at least one first heat exchangerin thermal communication with at least a first portion of a firstworking fluid. The first portion of the first working fluid flowsthrough the at least one thermoelectric assembly. The at least onethermoelectric assembly further comprises a plurality of thermoelectricelements in thermal communication with the at least one first heatexchanger. The at least one thermoelectric assembly further comprises atleast one second heat exchanger in thermal communication with theplurality of thermoelectric elements and with a second working fluidflowing through the at least one thermoelectric assembly. The secondworking fluid is cooler than the first working fluid. The thermoelectricpower generating system further comprises at least one heat exchangerportion configured to have at least some of the first portion of thefirst working fluid flow through the at least one heat exchanger portionafter having flowed through the at least one thermoelectric assembly.The at least one heat exchanger portion is configured to recover heatfrom the at least some of the first portion of the first working fluid.

In some embodiments, the at least one heat exchanger portion cancomprise a first conduit through which the at least some of the firstportion of the first working fluid flows. The at least one heatexchanger portion can further comprise a second conduit through which atleast a portion of the second working fluid flows. The second conduit isin thermal communication with the first conduit such that the portion ofthe second working fluid receives heat from the at least some of thefirst portion of the first working fluid.

In some embodiments, the at least one thermoelectric assembly isconfigured to convert high-temperature heat of the first working fluidto electricity such that low-temperature heat of the first working fluidis received by the at least one heat exchanger portion.

In some embodiments, the thermoelectric power generating system cancomprise at least one bypass conduit. The thermoelectric powergenerating system further comprises at least one valve configured toselectively allow at least the first portion of the first working fluidto flow through the at least one first heat exchanger and to selectivelyallow at least a second portion of the first working fluid to flowthrough the bypass conduit.

In some embodiments, the at least one heat exchanger portion isconfigured to receive at least some of the second portion of the firstworking fluid after having flowed through the at least one bypassconduit and to recover heat from the at least some of the second portionof the first working fluid.

In some embodiments, the at least one valve can comprise a proportionalvalve.

In some embodiments, the at least one valve can comprise at least onecomponent that is sensitive to high temperatures, and the at least onecomponent is in thermal communication with the second working fluid.

In some embodiments, the first working fluid can comprise exhaust gasfrom an engine. The at least one heat exchanger portion is furtherconfigured to use the recovered heat to warm at least one of an engineblock of the engine and a catalytic converter of the engine.

In some embodiments, the thermoelectric power generating system canfurther comprise at least one second heat exchanger portion configuredto have at least the first portion of the first working fluid flowthrough the at least one second heat exchanger portion prior to flowingthrough the at least one thermoelectric assembly. The at least onesecond heat exchanger portion is configured to reduce a temperature ofthe first portion of the first working fluid.

In some embodiments, the first working fluid can comprise exhaust gasfrom an engine. The at least one thermoelectric assembly is integratedinto at least one muffler of the engine.

In certain embodiments, a method of generating electricity is providedcomprising receiving at least a first portion of a first working fluid.The method further comprises flowing the first portion of the firstworking fluid through at least one thermoelectric assembly andconverting at least some heat from the first portion of the firstworking fluid to electricity. The method further comprises receiving atleast some of the first portion of the first working fluid after havingflowed through the at least one thermoelectric assembly. The methodfurther comprises recovering at least some heat from the at least someof the first portion of the first working fluid.

In some embodiments, converting at least some heat from the firstportion of the first working fluid to electricity can compriseconverting high-temperature heat from the first working fluid toelectricity. Recovering at least some heat from the at least some of thefirst portion of the first working fluid can comprise recoveringlow-temperature heat of the first working fluid.

In some embodiments, the method can further comprise selectivelyallowing at least the first portion of the first working fluid to flowthrough the at least one thermoelectric assembly and selectivelyallowing at least a second portion of the first working fluid to notflow through the at least one thermoelectric assembly.

In some embodiments, the first working fluid can comprise an exhaust gasfrom an engine. The method further comprises using the recovered heat towarm at least one of an engine block of the engine and a catalyticconverter of the engine.

In some embodiments, the method can further comprise reducing atemperature of the first portion of the first working fluid prior toflowing through the at least one thermoelectric assembly.

In certain embodiments, a thermoelectric power generation system isprovided comprising at least one thermoelectric assembly and a firstflow path with a first flow resistance. The first flow path through theat least one thermoelectric assembly. The system further comprises asecond flow path with a second flow resistance lower than the first flowresistance. The second flow path bypasses the at least onethermoelectric assembly. The system further comprises at least one valveconfigured to vary a first amount of a working fluid flowing along thefirst flow path and a second amount of the working fluid flowing alongthe second flow path.

In some embodiments, the system can further comprise at least oneconduit comprising at least one wall portion having a plurality ofperforations. The first flow path extends through the plurality ofperforations.

In some embodiments, the at least one conduit can further comprises aninlet and an outlet. The at least one valve is between the inlet and theoutlet.

In some embodiments, the at least one wall portion can further comprisea first wall portion with a first plurality of perforations and a secondwall portion with a second plurality of perforations. The at least onevalve between the first wall portion and the second wall portion. Thefirst flow path extends through the first plurality of perforationsoutwardly from the at least one conduit and through the second pluralityof perforations inwardly to the at least one conduit. The second flowpath does not extend through the first plurality of perforations and notthrough the second plurality of perforations.

In some embodiments, the at least one valve can comprise a proportionalvalve. In some embodiments, the at least one valve can comprise a flapvalve.

In some embodiments, the at least one thermoelectric assembly isintegrated in a muffler of an engine exhaust system.

In certain embodiments, a method of generating electricity is providedcomprising receiving a working fluid and selectively flowing at least aportion of the working fluid either along a first flow path having afirst flow resistance or along a second flow path having a second flowresistance lower than the first flow resistance. The first flow pathextends through at least one thermoelectric assembly. The second flowpath does not extend through the at least one thermoelectric assembly.

In some embodiments, the first flow path extends through a plurality ofperforations of at least one wall portion of at least one conduit.

In some embodiments, the at least one wall portion can further comprisea first wall portion with a first plurality of perforations and a secondwall portion with a second plurality of perforations. The first flowpath extends through the first plurality of perforations outwardly fromthe at least one conduit and through the second plurality ofperforations inwardly to the at least one conduit.

The paragraphs above recite various features and configurations of oneor more of a thermoelectric assembly, a thermoelectric module, or athermoelectric system, that have been contemplated by the inventors. Itis to be understood that the inventors have also contemplatedthermoelectric assemblies, thermoelectric modules, and thermoelectricsystems which comprise combinations of these features and configurationsfrom the above paragraphs, as well as thermoelectric assemblies,thermoelectric modules, and thermoelectric systems which comprisecombinations of these features and configurations from the aboveparagraphs with other features and configurations disclosed in thefollowing paragraphs.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are depicted in the accompanying drawings forillustrative purposes, and should in no way be interpreted as limitingthe scope of the thermoelectric assemblies or systems described herein.In addition, various features of different disclosed embodiments can becombined with one another to form additional embodiments, which are partof this disclosure. Any feature or structure can be removed, altered, oromitted. Throughout the drawings, reference numbers may be reused toindicate correspondence between reference elements.

FIG. 1A schematically illustrates an example thermoelectric powergenerating system.

FIG. 1B schematically illustrates an example thermoelectric powergenerating system with a heat exchanger portion engaged to a bypassconduit.

FIG. 2 schematically illustrates an example thermoelectric powergenerating system with a pre-heat exchanger portion.

FIG. 3 schematically illustrates a cross-sectional view of an exampleheat exchanger portion.

FIG. 4 schematically illustrates a cross-sectional view of an exampleheat exchanger portion.

FIGS. 5A-5B schematically illustrate two example thermoelectric powergenerating systems.

FIG. 6 schematically illustrates an example thermoelectric powergenerating system having at least one TEG device integrated into amuffler.

FIG. 7 schematically illustrates another example thermoelectric powergenerating system having at least one TEG device integrated into amuffler.

FIG. 8 schematically illustrates another example thermoelectric powergenerating system having at least one TEG device integrated into amuffler.

FIG. 9A schematically illustrates an example thermoelectric powergenerating system having a multiple-shell muffler.

FIG. 9B schematically illustrates an example thermoelectric powergenerating system having a coolant routing integrated into amultiple-shell muffler.

FIG. 9C schematically illustrates a cross-sectional view of thethermoelectric power generating system of FIG. 9A.

FIG. 10 schematically illustrates an example thermoelectric powergenerating system having at least one Helmholtz resonator.

FIG. 11 schematically illustrates an example thermoelectric powergenerating system having at least one TEG device integrated into amuffler.

FIG. 12 is a flow diagram of an example method of generatingelectricity.

FIG. 13 is a flow diagram of another example method of generatingelectricity.

FIG. 14 schematically illustrates some external features an examplethermoelectric power generating system.

FIGS. 15A-15B schematically illustrate some internal features an examplethermoelectric power generating system.

FIG. 16A-16C schematically illustrate an example thermoelectric powergenerating system having a valve in three different positions.

DETAILED DESCRIPTION

Although certain embodiments and examples are disclosed herein, thesubject matter extends beyond the examples in the specifically disclosedembodiments to other alternative embodiments and/or uses, and tomodifications and equivalents thereof. Thus, the scope of the claimsappended hereto is not limited by any of the particular embodimentsdescribed below. For example, in any method or process disclosed herein,the acts or operations of the method or process may be performed in anysuitable sequence and are not necessarily limited to any particulardisclosed sequence. Various operations may be described as multiplediscrete operations in turn, in a manner that may be helpful inunderstanding certain embodiments; however, the order of descriptionshould not be construed to imply that these operations are orderdependent. Additionally, the structures, systems, and/or devicesdescribed herein may be embodied as integrated components or as separatecomponents. For purposes of comparing various embodiments, certainaspects and advantages of these embodiments are described. Notnecessarily all such aspects or advantages are achieved by anyparticular embodiment. Thus, for example, various embodiments may becarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otheraspects or advantages as may also be taught or suggested herein.

A thermoelectric system as described herein comprise a thermoelectricgenerator (TEG) which uses the temperature difference between twofluids, two solids (e.g., rods), or a solid and a fluid to produceelectrical power via thermoelectric materials. Alternatively, athermoelectric system as described herein can comprise a heater, cooler,or both which serves as a solid state heat pump used to move heat fromone surface to another, thereby creating a temperature differencebetween the two surfaces via the thermoelectric materials. Each of thesurfaces can be in thermal communication with or comprise a solid, aliquid, a gas, or a combination of two or more of a solid, a liquid, anda gas, and the two surfaces can both be in thermal communication with asolid, both be in thermal communication with a liquid, both be inthermal communication with a gas, or one can be in thermal communicationwith a material selected from a solid, a liquid, and a gas, and theother can be in thermal communication with a material selected from theother two of a solid, a liquid, and a gas.

The thermoelectric system can include a single thermoelectric assembly(e.g., a single TE cartridge) or a group of thermoelectric assemblies(e.g., a group of TE cartridges), depending on usage, power output,heating/cooling capacity, coefficient of performance (COP) or voltage.Although the examples described herein may be described in connectionwith either a power generator or a heating/cooling system, the describedfeatures can be utilized with either a power generator or aheating/cooling system. Examples of TE cartridges compatible withcertain embodiments described herein are provided by U.S. Pat. Appl.Publ. No. 2013/0104953, filed Jun. 5, 2012 and U.S. patent applicationSer. No. 13/794,453, filed Mar. 11, 2013, each of which is incorporatedin its entirety by reference herein.

The term “thermal communication” is used herein in its broad andordinary sense, describing two or more components that are configured toallow heat transfer from one component to another. For example, suchthermal communication can be achieved, without loss of generality, bysnug contact between surfaces at an interface; one or more heat transfermaterials or devices between surfaces; a connection between solidsurfaces using a thermally conductive material system, wherein such asystem can include pads, thermal grease, paste, one or more workingfluids, or other structures with high thermal conductivity between thesurfaces (e.g., heat exchangers); other suitable structures; orcombinations of structures. Substantial thermal communication can takeplace between surfaces that are directly connected (e.g., contact eachother) or indirectly connected via one or more interface materials.

As used herein, the terms “shunt” and “heat exchanger” have theirbroadest reasonable interpretation, including but not limited to acomponent (e.g., a thermally conductive device or material) that allowsheat to flow from one portion of the component to another portion of thecomponent. Shunts can be in thermal communication with one or morethermoelectric materials (e.g., one or more thermoelectric elements) andin thermal communication with one or more heat exchangers of thethermoelectric assembly or system. Shunts described herein can also beelectrically conductive and in electrical communication with the one ormore thermoelectric materials so as to also allow electrical current toflow from one portion of the shunt to another portion of the shunt(e.g., thereby providing electrical communication between multiplethermoelectric materials or elements). Heat exchangers (e.g., tubesand/or conduits) can be in thermal communication with the one or moreshunts and one or more working fluids of the thermoelectric assembly orsystem. Various configurations of one or more shunts and one or moreheat exchangers can be used (e.g., one or more shunts and one or moreheat exchangers can be portions of the same unitary element, one or moreshunts can be in electrical communication with one or more heatexchangers, one or more shunts can be electrically isolated from one ormore heat exchangers, one or more shunts can be in direct thermalcommunication with the thermoelectric elements, one or more shunts canbe in direct thermal communication with the one or more heat exchangers,an intervening material can be positioned between the one or more shuntsand the one or more heat exchangers). Furthermore, as used herein, thewords “cold,” “hot,” “cooler,” “hotter” and the like are relative terms,and do not signify a particular temperature or temperature range.

Certain embodiments described herein provide a thermoelectric powergenerating (TEG) system comprising at least one thermoelectric subsystemand at least one heat exchanger (or portion thereof) in thermalcommunication with the at least one thermoelectric subsystem.

For example, the at least one thermoelectric subsystem can comprise atleast one “cartridge-based thermoelectric system” or “cartridge” with atleast one thermoelectric assembly 10 or at least one thermoelectricsystem as disclosed in U.S. Pat. Appl. Publ. No. 2013/0104953, which isincorporated in its entirety by reference herein. The cartridge isconfigured to apply a temperature differential across an array ofthermoelectric elements 30, 40 of the cartridge in accordance withcertain embodiments described herein. FIG. 6B of U.S. Pat. Appl. Publ.No. 2013/0104953 illustrates a perspective cross-sectional view of anexample cartridge compatible with certain embodiments described herein.The cartridge of this figure includes an anodized aluminum “cold side”tube or conduit which is in thermal communication with a plurality ofthermoelectric elements and a plurality of “hot side” heat transferassemblies in thermal communication with the plurality of thermoelectricelements, such that a temperature differential is applied across thethermoelectric elements. As described in U.S. Pat. Appl. Publ. No.2013/0104953 regarding certain configurations, the “hot side” heattransfer assemblies can have a first working fluid (e.g., gas or vapor)flowing across the “hot side” heat transfer assemblies and the “coldside” tube can have a second working fluid (e.g., water) flowing throughit.

In certain embodiments, the at least one heat exchanger comprises atleast one heat pipe or at least one thermosyphon. For example, the atleast one heat pipe or at least one thermosyphon can replace the “coldside” tube of the cartridge of FIG. 6B of U.S. Pat. Appl. Publ. No.2013/0104953. As used herein, the term “heat pipe” has its broadestreasonable interpretation, including but not limited to a device thatcontains a material in a first phase (e.g., a liquid) that is configured(i) to absorb heat at a first position within the device and to change(e.g., evaporate) into a second phase (e.g., gas or vapor) and (ii) tomove while in the second phase from the first position to a secondposition within the device, (iii) to emit heat at the second positionand to change back (e.g., condense) into the first phase, and (iv) toreturn while in the first phase to the first position. As used herein,the term “thermosyphon” has its broadest reasonable interpretation,including but not limited to a device that contains a material (e.g.,water) that is configured (i) to absorb heat at a first position withinthe device, (ii) to move from the first position to a second positionwithin the device, (iii) to emit heat at the second position. Forexample, the material within the thermosyphon can circulate between thefirst position and the second position passively (e.g., without beingpumped by a mechanical liquid pump) to provide convective heat transferfrom the first position to the second position. In certain embodiments,the at least one heat exchanger can utilize gravity or can otherwise beorientation-dependent. In certain embodiments, the at least one heatexchanger does not comprise any moving parts (except the material movingbetween the first and second positions), and can be characterized asproviding passive energy transfer or heat exchange.

TEG Portion and HEX Portion

FIGS. 1A and 1B schematically illustrate example TEG systems inaccordance with certain embodiments described herein. The TEG system 100comprises a thermoelectric subsystem (e.g., a TEG portion 13 such as oneor more TE cartridges) and a heat exchanger (HEX) portion 15 (e.g., influidic communication with the TEG portion 13, in thermal communicationwith the TEG portion 13, or both). In some embodiments, the example TEGsystems 100 of FIGS. 1A and 1B also comprise at least one valve 17 thatcan allow flow of at least a portion of the first working fluid (e.g.,gas as indicated by arrow 19) through the TEG portion 13, with anyremaining portion of the first working fluid (as indicated by arrow 21)flowing through a bypass 23 as discussed in accordance with certainembodiments herein.

In some embodiments, a TEG system 100 is provided that comprises atleast one thermoelectric assembly 10 (e.g., at least one TEG portion 13such as one or more TE cartridges as disclosed in U.S. Pat. Appl. Publ.No. 2013/0104953). The at least one thermoelectric assembly 10 comprisesat least one first heat exchanger 50 in thermal communication with atleast a first portion of a first working fluid (e.g., hot-side fluid,gas, vapor as indicated by arrow 19). The first portion of the firstworking fluid flows through the at least one thermoelectric assembly 10.The at least one thermoelectric assembly 10 further comprises aplurality of thermoelectric elements 30, 40 (e.g., n-type and/or p-type)in thermal communication with the at least one first heat exchanger 50.The at least one thermoelectric assembly 10 further comprises at leastone second heat exchanger (e.g., thermally conductive conduit or tube102 and/or shunts 110) in thermal communication with the plurality ofthermoelectric elements 30, 40 and with a second working fluid (e.g.,cold-side fluid, gas, vapor, water) flowing through the at least onethermoelectric assembly 10. The second working fluid is cooler than thefirst working fluid. The TEG system 100 further comprises at least oneheat exchanger portion 15 configured to have at least some of the firstportion of the first working fluid flow through the at least one heatexchanger portion 15 after having flowed through the at least onethermoelectric assembly 10. The at least one heat exchanger portion 15is configured to recover heat from the at least some of the firstportion of the first working fluid as discussed below.

In some embodiments, the at least one thermoelectric assembly 10 (e.g.,the at least one TEG portion 13) can be located in a region having ahigh temperature differential between the first working fluid and theenvironment of the at least one thermoelectric assembly 10, therebyproviding a high thermoelectric efficiency. The at least one heatexchanger portion 15 can be in fluidic communication with the TEGportion 13 (e.g., downstream of the TEG portion 13) and dedicated to aparticular use of the heat of the first working fluid that is notconverted into electricity by the TEG portion 13.

For example, as schematically illustrated by FIG. 1A, the at least onethermoelectric assembly 10 may not convert all of the heat of the firstworking fluid (e.g., exhaust gas, hot fluid, first working fluid asindicated by arrow 19) into electricity, so the at least some of thefirst working fluid flowing out of the at least one thermoelectricassembly 10 and through the at least one heat exchanger portion 15 canbe used by the at least one heat exchanger portion 15 for a particularpurpose. The at least one thermoelectric assembly 10 may only be able toeffectively convert “high quality” or “high temperature” heat of thefirst working fluid into electricity, so the “low quality” or “lowtemperature” heat that is not converted can be utilized for a particularpurpose by the at least one heat exchanger portion 15, resulting in anoverall increase of efficiency. In some embodiments, the at least onethermoelectric assembly 10 is configured to convert high-temperatureheat of the first working fluid to electricity such that low-temperatureheat of the first working fluid is received by the at least one heatexchanger portion 15. For example, the heat extracted from the firstworking fluid by the at least one thermoelectric assembly 10 can be lessthan or equal to a predetermined percentage (e.g., 40%, 50%, 60%, 70%)of the total amount of extractable or usable heat carried by the firstworking fluid to the at least one thermoelectric assembly 10, and the atleast one heat exchanger portion 15 can be configured (e.g., optimized)to utilize (e.g., extract) some or all of the remaining portion (e.g.,60%, 50%, 40%, 30%) of the total amount of extractable or usable heatcarried by the first working fluid to the at least one thermoelectricassembly 10).

As another example, as schematically illustrated by FIG. 1B, undercertain conditions (e.g., having a first working fluid comprising arelatively low temperature exhaust gas, such as at start-up of anengine), at least a portion of the first working fluid (as indicated byarrow 21) can be diverted from flowing through the at least onethermoelectric assembly 10 (which may not be efficient at theseconditions) but can be directed to the at least one heat exchangerportion 15 (e.g., via a bypass conduit 23) which receives and uses thefirst working fluid for a particular purpose.

Thus, the TEG system 100 can be configured to provide electrical powergeneration with high efficiency, and/or to provide recuperation (e.g.,recovery) of the residual (e.g., low quality or low temperature) heatwith high efficiency. In certain embodiments, the particular purpose forwhich the at least one heat exchanger portion 15 can use the low qualityor low temperature heat can comprise recovering heat and applying it toother portions of the engine. In some embodiments, the first workingfluid of the TEG system 100 comprises exhaust gas from an engine, andthe at least one heat exchanger portion 15 is further configured to userecovered heat to warm at least one of an engine block of the engine, acatalytic converter of the engine, or a passenger compartment (e.g.,cabin) of a vehicle. For example, at least a portion of the recoveredheat can be put into the cooling system of an engine to achieve fasterheating of the engine block at start-up (e.g., to warm up the oillubrication system sooner) and/or at least a portion of the recoveredheat can be put into the emission system to achieve faster heating orengagement of the catalytic converter to reach the “light-off”temperature sooner after start-up, thereby reducing overall emissionsand/or at least a portion of the recovered heat can be used to improvethe thermal comfort of the cabin to the driver and passengers of avehicle. In certain such embodiments, the at least one heat exchangerportion 15 can comprise a first conduit through which the at least someof the first portion of the first working fluid flows and a secondconduit through which at least a portion of the second working fluidflows. The second conduit can be in thermal communication with the firstconduit such that the portion of the second working fluid receives heatfrom the at least some of the first portion of the first working fluid.In certain embodiments, the at least one thermoelectric assembly 10 andthe at least one heat exchanger 15 can both utilize the same secondworking fluid.

As illustrated and disclosed with respect to FIGS. 1A and 1B, in someembodiments, the TEG system 100 further comprises at least one bypassconduit 23 and at least one valve 17. The at least one valve 17 isconfigured to selectively allow at least the first portion of the firstworking fluid (as indicated by arrow 19) to flow through the at leastone first heat exchanger 50 and to selectively allow at least a secondportion of the first working fluid (as indicated by arrow 21) to flowthrough the bypass conduit 23. In some embodiments, as illustrated inFIG. 1B, the at least one heat exchanger portion 15 is configured toreceive at least some of the second portion of the first working fluidafter having flowed through the at least one bypass conduit 23 and torecover heat from the at least some of the second portion of the firstworking fluid. For example, in some embodiments, a portion of at leastone heat exchanger portion 15 can be in fluidic and/or thermalcommunication with the bypass conduit 23.

While the example TEG systems 100 of FIGS. 1A and 1B have the at leastone valve 17 positioned upstream of the at least one thermoelectricassembly 10 and the at least one heat exchanger portion 15, otherembodiments can have the at least one valve 17 positioned downstream ofthe at least one thermoelectric assembly 10 and the at least one heatexchanger portion 15 or between the at least one heat exchanger portion15 and the at least one thermoelectric assembly 10. The at least onevalve 17 can comprise one or more valves selected from the groupconsisting of a multi-port valve and a proportional valve. The at leastone valve 17 can determine whether the at least one thermoelectricassembly 10 only is engaged (e.g., the first working fluid flows throughthe at least one thermoelectric assembly 10 but not through the at leastone heat exchanger portion 15), the at least one heat exchanger portion15 only is engaged (e.g., the first working fluid flows through the atleast one heat exchanger portion 15 but not through the at least onethermoelectric assembly 10), or both the at least one thermoelectricassembly 10 and the at least one heat exchanger portion 15 are engaged(e.g., the first working fluid flows through both the at least onethermoelectric assembly 10 and the at least one heat exchanger portion15). The at least one heat exchanger portion 15 can be engaged with theat least one bypass conduit 23, in addition to being engaged to theprimary gas flow (as indicated by arrow 19), as schematicallyillustrated by FIG. 1B.

FIG. 2 schematically illustrates another example TEG system 100 inaccordance with certain embodiments described herein. In someembodiments, the TEG system 100 comprises at least one second heatexchanger portion 25 (e.g., located upstream of the at least onethermoelectric assembly 10) configured to have at least the firstportion of the first working fluid (as indicated by arrow 19) flowthrough the at least one second heat exchanger portion 25 prior toflowing through the at least one thermoelectric assembly 10. The atleast one second heat exchanger portion 25 can be configured to reduce atemperature of the first portion of the first working fluid.

For example, as illustrated in FIG. 2, the at least one second heatexchanger portion 25 is located upstream of the at least onethermoelectric assembly 10 in order to decrease the temperature of theflowing first working fluid as indicated by arrow 19 prior to flowingthrough the at least one thermoelectric assembly 10 (e.g., forapplications in which the temperature of the first working fluid wouldbe too high for the TE materials of the at least one thermoelectricassembly 10). Possible advantages of such an example TEG system 100include, but are not limited to, protection of the TE material orelements from overheating (e.g., excessive temperatures), electricalpower generation with high efficiency, and/or recuperation of theresidual heat with high efficiency.

A method 300 for generating electricity according to certain embodimentsdescribed herein is illustrated in the flow diagram of FIG. 12. Whilethe method 300 is described below by referencing the structuresdescribed above, the method 300 may also be practiced using otherstructures. In an operational block 310, the method 300 comprisesreceiving at least a portion of a first working fluid. In an operationalblock 320, the method 300 further comprises flowing the first portion ofthe first working fluid through at least one thermoelectric assembly 10and converting at least some heat from the first portion of the firstworking fluid to electricity. In an operational block 330, the method300 further comprises receiving at least some of the first portion ofthe first working fluid after having flowed through the at least onethermoelectric assembly 10. In an operational block 340, the method 300further comprises recovering at least some heat from the at least someof the first portion of the first working fluid (e.g., using the atleast one heat exchanger portion 15).

In some embodiments, converting at least some heat from the firstportion of the first working fluid to electricity comprises convertinghigh-temperature heat from the first working fluid to electricity.Further, recovering at least some heat from the at least some of thefirst portion of the first working fluid comprises recoveringlow-temperature heat of the first working fluid.

In some embodiments, the method 300 of generating electricity furthercomprises selectively allowing at least the first portion of the firstworking fluid to flow through the at least one thermoelectric assembly10 and selectively allowing at least a second portion of the firstworking fluid to not flow through the at least one thermoelectricassembly 10 (e.g., through at least one bypass conduit 23).

In some embodiments, the first working fluid comprises an exhaust gasfrom an engine and the method further comprises using the recovered heatto warm at least one of an engine block of the engine and a catalyticconverter of the engine.

In some embodiments, the method 300 of generating electricity furthercomprises reducing a temperature of the first portion of the firstworking fluid prior to flowing through the at least one thermoelectricassembly 10 (e.g., using at least one second heat exchanger portion 25).

Temperature-Activated Heat Exchanger

Regarding the overheating protection, in TEG operation, there is often alimit to the temperatures that the TE material can withstand.Unfortunately, in extreme situations, the exhaust gas temperatures canbe excessive and can cause the TE surface temperature to exceed itslimit unless it is regulated. To prevent the TE material fromoverheating, some or all of the exhaust flow can be bypassed (e.g., bedirected away) from the TE material. However, such an embodiment maybypass more potentially valuable heat than is necessary or desirable.For example, all of the heat may be bypassed when the flow is bypassed,as opposed to just the high quality or high temperature heat.

In certain embodiments described herein, the TE surface temperature canbe controlled by dissipating the excessive heat prior to entering the atleast one thermoelectric assembly 10. The remainder of the heat in theexhaust flow could then continue into the at least one thermoelectricassembly 10, thereby preventing the unnecessary bypass of valuable heat.

Certain embodiments described herein advantageously only dissipate heatwhen there is an excess amount of heat. FIGS. 3 and 4 schematicallyillustrate cross-sectional view of example heat exchanger portions 26 inaccordance with certain embodiments described herein. The heat exchangerportion 26 can be located upstream from the at least one thermoelectricassembly 10 and in series with at least one thermoelectric assembly 10(e.g., the first working fluid flows through the heat exchanger portion26 prior to flowing through the at least one thermoelectric assembly10). For example, the at least one heat exchanger portion 25 describedabove can comprise the heat exchanger portion 26. In certainembodiments, the heat exchanger portion 26 can dissipate relativelylittle heat at low temperatures, can use heat pipe technology to beactivated at higher temperatures to dissipate excess heat withoutbypassing valuable flow, and can be a passive way to provide TEGovertemperature or overheating protection. FIGS. 3 and 4 schematicallyillustrate some example embodiments and do not represent all of therelated embodiments that could be employed in accordance with certainembodiments described herein. Furthermore, the heat exchanger portion 26can be used in a TEG system that also includes the structures describedabove with regard to FIGS. 1A, 1B, and 2.

As schematically illustrated in FIG. 3, the heat exchanger portion 26can comprise a central region 19 (e.g., conduit) and at least one heatpipe 27 (e.g., a first annular region concentric with the central region19). The central region 19 can be configured to allow the exhaust gas toflow through (e.g., in a direction generally perpendicular to the planeof the cross-sectional view in FIG. 3). The at least one heat pipe 27can be configured to contain a high-temperature fluid 31. An inner wall33 of the heat pipe 27 can be in thermal communication with the exhaustgas and an outer wall 35 of the heat pipe 27 can be in thermalcommunication with an outer region 21 (e.g., a second concentric annularregion bounded by a second conduit, as schematically illustrated in FIG.3). The high-temperature fluid 31 can be configured to undergoevaporation at the inner wall 33 (e.g., in thermal communication withthe exhaust gas at a first temperature) and can be configured to undergocondensation at the outer wall 35 (e.g., in thermal communication withthe outer region 21 at a second temperature less than the firsttemperature).

For example, the outer region 21 (e.g., the second concentric annularregion bounded by the second conduit) can be configured to allow acoolant (e.g., gas or liquid) to flow through (e.g., in a directiongenerally perpendicular to the plane of the cross-sectional view in FIG.3). While FIG. 3 shows the central region 19, the heat pipe 27, andouter region 21 being generally circular and generally concentric withone another, other shapes and configurations (e.g., non-concentric) arealso compatible with certain embodiments described herein. In otherembodiments, the outer region 21 can comprise a heat sink (e.g., adevice that dissipates at least a portion of the heat from thehigh-temperature fluid).

In certain embodiments, the heat pipe 27 can be used to provide atemperature-activated heat exchanger. The evaporator portion of the heatpipe or thermal plane could work above a certain temperature (e.g., 700C), for example, using one or more high-temperature heat pipe fluids 31,such as Li, Na, K, and Cs, which are known in the art. In certainembodiments, at low temperatures (e.g., before the high temperaturecondition is reached), the heat transfer is poor, based on naturalconvection of the high-temperature fluid. Once activated, the heatexchanger portion 26 of certain embodiments can use the high heattransfer capability of boiling and condensing to transfer heat. Forexample, heat transfer coefficients can go up by a factor of 100 fromthe low temperature regime to the high temperature regime.

FIG. 4 schematically illustrates a cross-sectional view of anotherexample heat exchanger portion 26 in accordance with certain embodimentsdescribed herein. The at least one heat pipe 27 can extend from thecentral region 19 containing the exhaust gas to the outer region 21containing the coolant or heat sink. For example, a first portion 37 ofthe at least one heat pipe 27 can be in thermal communication with theexhaust gas and a second portion 39 of the at least one heat pipe 27 canbe in thermal communication with the coolant or heat sink. A region 41between the central region 19 and the outer region 21 can besubstantially thermally insulating (e.g., can contain gas or air), orcan contain another material. In certain embodiments, the at least oneheat pipe 27 can comprise one or more generally cylindrical heat pipes(e.g., a series of cylindrical heat pipes), while in certain otherembodiments, the at least one heat pipe can comprise one or moregenerally planar heat pipes extending along the axis of the heatexchanger portion 26 (e.g., along a direction generally perpendicular tothe cross-sectional view of FIG. 4).

Protecting Temperature-Sensitive Components

FIGS. 5A and 5B schematically illustrate two example TEG systems 100comprising temperature-sensitive components in accordance with certainembodiments described herein. In some embodiments, the TEG system 100can comprise at least one valve 17 that comprises at least one componentthat is sensitive to high temperatures, and the at least one componentis in thermal communication with the second working fluid (e.g., flowingthrough a coolant circuit 51 of the TEG system 100). In certainembodiments, the TEG system 100 takes advantage of available coldersurfaces (e.g., due to the presence of a coolant circuit 51 configuredto have the second working fluid flow therethrough) in order to protecttemperature-sensitive components (e.g., temperature-sensitive valvesub-components, such as the actuator 53 and the electronics 55). Thetemperature-sensitive components can be used to move, control or actuatethe at least one valve 17 or a drive shaft or flexible wire 57 connectedto the valve 17. For example, the TEG system 100 can keep suchtemperature-sensitive components below a predetermined temperature(e.g., below 150 C). In certain embodiments, the TEG system 100 cancomprise a phase-change material located between the coolant circuit 51and the temperature-sensitive components (e.g., electronics 55) tofurther protect against temperature spikes. Having the at least onevalve 17 in thermal communication with the coolant circuit 51 can beused in a TEG system 100 that also includes one or more of thestructures described above with regard to FIGS. 1-4.

Thermoelectric Assemblies Integrated into a Muffler

In certain embodiments, the TEG system 100 can integrate at least onethermoelectric assembly 10 with acoustic dampening components (e.g.,mufflers). FIG. 6 schematically illustrates an example TEG system 100comprising at least one thermoelectric assembly 10 (e.g., one or morecartridges) integrated into a muffler 59, in accordance with certainembodiments described herein. In some embodiments, the first workingfluid of such a TEG system 100 comprises exhaust gas 75 from an engineas discussed above. The at least one thermoelectric assembly 10 isintegrated into at least one muffler 59 of the engine exhaust system.For example, the at least one thermoelectric assembly 10 can bepositioned between two muffler baffles 61, 63, and additional mufflerchambers can be used to achieve the desired acoustic performance. Incertain embodiments, the at least one thermoelectric assembly 10 can bepositioned in a first chamber (e.g., inlet chamber 65) to reducetemperature loss before the at least one thermoelectric assembly 10. Thegas can stream into the first chamber through a perforation field 67(see, e.g., FIG. 6) or directly into the first chamber. An additionaldeflecting plate could be used to get a homogeneous flow distribution tothe at least one thermoelectric assembly 10. The gas can stream out ofthe muffler 59 through a second chamber (e.g., outlet chamber 66).

FIG. 7 schematically illustrates another example TEG system 100comprising at least one thermoelectric assembly 10 (e.g., one or morecartridges) integrated into a muffler 59, in accordance with certainembodiments described herein. The TEG system 100 comprises at least onespring-forced valve 69 (e.g., having mechanical control) between thechambers (e.g., at the inner baffle 63 of the muffler) which isconfigured to open at a predetermined condition (e.g., the maximum massflow/temperature conditions) to allow the exhaust gas to bypass the atleast one thermoelectric assembly 10 and to avoid overheating of the atleast one thermoelectric assembly 10. The at least one valve 69 can betuned appropriately be selection of the spring force and thecross-sectional area through which exhaust gas can flow. For example,these parameters can be selected based on system-level constraints orrequirements such as the maximum engine back-pressure and the exhaustgas flow rate at which the maximum engine back-pressure is to occur.

FIG. 8 schematically illustrates another example TEG system 100comprising at least one thermoelectric assembly 10 (e.g., one or morecartridges) integrated into a muffler 59, in accordance with certainembodiments described herein. The TEG system 100 can be configured toprotect various components, such as the electrical cables 71 and coolant(e.g., water) pipes 73, against environment conditions and to have themcovered to avoid damage caused by any other objects. In certainembodiments, the cabling and tubing are not visible from outside themuffler 59. In certain embodiments, the TEG system 100 can compriseacoustic material downstream of the at least one thermoelectric assembly10. Other benefits can include, but are not limited to, lowertemperatures of the acoustic material, lower flow velocities, and thepotential to use lower cost and weight canning/shell (e.g., plasticversus metal) due to the lower temperatures. Integration of the at leastone thermoelectric assembly 10 with a muffler as described above can beused in a TEG system 100 that also includes one or more of thestructures described above with regard to FIGS. 1-5.

Multiple-Shell Muffler

FIG. 9A schematically illustrates an example TEG system 100 comprising amultiple-shell muffler 77 in which an inner shell 79 contains at leastone thermoelectric assembly 10 (e.g., one or more cartridges) and anouter shell 81 contains components (e.g., electrical cables, coolantpipes, tubes, or conduits), portions of which are outside the innershell 79 and that are to be protected, in accordance with certainembodiments described herein. FIG. 9C schematically illustrates across-sectional view of the example TEG system 100 of FIG. 9A in theplane indicated by arrows. Certain embodiments advantageously integratemultiple functions into the shells of the muffler 77. One or all of themuffler shells can be a stamped part so that the geometry can be designflexible.

In certain embodiments, the inner shell 79 contains or carries the atleast one thermoelectric assembly 10 and the outer shell 81 (e.g., covershell) contains, supports, and protects the electrical cables andcoolant (e.g., water) pipes. For a controlled routing of the pipes andtheir fixation, the shell design can be formed accordingly. Variousconfigurations are also compatible with certain embodiments describedherein. For example, the TEG system 100 can comprise an inner shell 79for the at least one thermoelectric assembly 10 and inner baffles thatcan provide the desired acoustic reduction. A catalytic converter can beintegrated into the inner shell 79 (e.g., upstream of the at least onethermoelectric assembly). The TEG system 100 can comprise a first (e.g.,inner) shell 79 for the TE cartridges, a second shell containing athermal insulation material 83, and a third (e.g., outer) shell 81containing the electrical cabling and coolant (e.g., water) routing.

Coolant channels can be formed into the half-shell design withoutseparate coolant tubing. FIG. 9B schematically illustrates an exampleTEG system 100 in which coolant (e.g., water) routing is integrated intothe multiple-shell muffler 77, in accordance with certain embodimentsdescribed herein. The TEG system 100 can comprise an inner shell 79, amiddle shell 83, and an outer shell 81. In certain embodiments, thecoolant (e.g., water) routing is in the outer shell 81 (e.g., betweenthe middle shell 83 and the outer shell 81), and the electrical cables89 are routed in the middle shell 83 (e.g., between the middle shell 83and the inner shell 79) or on the surface of the middle shell 83. Insome embodiments, the coolant enters through one or more inlets 85 andexits through one or more outlets 87 in the outer shell 81. Certainembodiments further comprise an insulation mat 91 between the cartridgesupport shell (e.g., inner shell 79) and the middle shell 83. Theinsulation mat 91 can provide one or more of the following functions:(i) heat protection of the cables 89 and the coolant conduit (e.g.,manifold 93); (ii) noise reduction of the muffler to the environment;(iii) reduction of the outer surface temperature; and (iv) reduction ofthermal losses. The multiple-shell muffler can be used in a TEG system100 that also includes one or more of the structures described abovewith regard to FIGS. 1-8.

Integration of Bypass and Helmholtz Resonator

FIG. 10 schematically illustrates an example TEG system 100 comprising abypass 103, at least one thermoelectric assembly 10, and at least oneHelmholtz resonator 105. Helmholtz resonators are often used in ofexhaust systems, in order to dampen low frequency engine noises, or tomitigate noise peaks at specific frequencies. The bypass 103 can bedesigned in order to act as a Helmholtz resonator when the valve 107 isclosed (e.g., by adding an expansion chamber). The large volume of airin the chamber can serve as the spring and the air in the neck can serveas the oscillating mass. The working fluid 75 (e.g., exhaust, air) canenter through an inlet 78 and exit through an outlet 80 as indicated bythe arrows. The at least one Hemholtz resonator 105 can be used in a TEGsystem 100 that also includes one or more of the structures describedabove with regard to FIGS. 1-9.

Valve to Control Mass Flow

FIG. 11 schematically illustrates an example TEG system 200 inaccordance with certain embodiments described herein. In someembodiments, the TEG system 200 comprises at least one thermoelectricassembly 10 (e.g., TEG device, cartridge). The TEG system 200 furthercomprises a first flow path (indicated by arrows 203) with a first flowresistance. The first flow path 203 is through the at least onethermoelectric assembly 10. The TEG system 200 further comprises asecond flow path (indicated by arrows 205) with a second flow resistancelower than the first flow resistance. The second flow path bypasses theat least one thermoelectric assembly 10. The TEG system 200 furthercomprises at least one valve 201 (e.g., flap valve, proportional valve,three-way valve) configured to vary a first amount of a working fluid(e.g., exhaust) flowing along the first flow path and a second amount ofthe working fluid flowing along the second flow path.

For example, the at least one valve 201 can be controlled to vary thefirst amount (e.g., fraction) of the working fluid to be any valuebetween zero and 100% of the total amount of working fluid flowingthrough the TEG system 200 (e.g., 0%, 5%, 10%, 15%, 20%, 25%, 30%, 40%,50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 100%). The at least one valve201 can be controlled to vary the second amount (e.g., fraction) of theworking fluid to be any value between zero and 100% of the total amountof working fluid flowing through the TEG system 200 (e.g., 0%, 5%, 10%,15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 100%).

In some embodiments, the at least one thermoelectric assembly 10 isintegrated into a muffler of an engine exhaust system, in accordancewith certain embodiments described herein. In certain embodiments, theTEG system 200 can be designed in order to ensure 100% mass flow throughthe bypass (e.g., second flow path) when the valve 201 is open.

In some embodiments, the TEG system 200 further comprises at least oneconduit 207 comprising at least one wall portion 209 having a pluralityof perforations 211. The first flow path extends through the pluralityof perforations 211. In some embodiments, the at least one conduit 207further comprises an inlet 213 and an outlet 215, and the at least onevalve 201 is between the inlet 213 and the outlet 215

In some embodiments, the at least one wall portion 209 comprises a firstwall portion 209A with a first plurality of perforations 211A and asecond wall portion 209B with a second plurality of perforations 211B.The at least one valve 201 is positioned between the first wall portion209A and the second wall portion 209B. The first flow path extendsthrough the first plurality of perforations 211A outwardly from the atleast one conduit 207 and through the second plurality of perforations211B inwardly to the at least one conduit 207. The second flow path doesnot extend through the first plurality of perforations 211A and does notextend through the second plurality of perforations 211B.

For example, a flow path can be designed for the TEG branch in which theback-pressure field is higher than the pressure field in the bypass whenthe at least one valve 201 is open. While FIG. 11 schematicallyillustrates the first plurality of perforations 211A and the secondplurality of perforations 211B, other structures (e.g., by introducingflow bends) may be used instead to cause the flow resistance in the TEGbranch (e.g., first flow path) to be higher than the flow resistance inthe bypass (e.g., the second flow path). The flow path can also bedesigned to use the flow momentum to increase the flow passage in thebypass pipe (e.g., by using a straight pipe) when the valve is closed.Certain embodiments advantageously provide and utilize a simpler andcost-effective flap valve, instead of a three-way valve. Certainembodiments described herein can use one or more passive (e.g.,spring-actuated) valves or valves actuated by thermal wax actuatorsconnected to the coolant circuit. The at least one valve 201 can be usedin a TEG system 100 that also includes one or more of the structuresdescribed above with regard to FIGS. 1-10.

A method 400 for generating electricity according to certain embodimentsdescribed herein is illustrated in the flow diagram of FIG. 13. Whilethe method 400 is described below by referencing the structuresdescribed above, the method 400 may also be practiced using otherstructures. In an operational block 410, the method 400 comprisesreceiving a working fluid. In an operational block 420, the method 400further comprises selectively flowing at least a portion of the workingfluid either along a first flow path having a first flow resistance oralong a second flow path having a second flow resistance lower than thefirst flow resistance. The first flow path extends through at least onethermoelectric assembly 10 and the second flow path does not extendingthrough the at least one thermoelectric assembly 10.

In some embodiments, the first flow path extends through a plurality ofperforations 211 of at least one wall portion 209 of at least oneconduit 207.

In some embodiments, the at least one wall portion 209 comprises a firstwall portion 209A with a first plurality of perforations 211A and asecond wall portion 209B with a second plurality of perforations 211B.The first flow path extends through the first plurality of perforations211A outwardly from the at least one conduit 207 and through the secondplurality of perforations 211B inwardly to the at least one conduit 207.

Integrated Proportional Bypass Valve

Certain embodiments described herein provide a thermoelectric powergenerating (TEG) system 500 comprising at least one thermoelectricsubsystem 509 (e.g., at least one thermoelectric assembly 10) and atleast one bypass conduit 511. The TEG system 500 further comprises atleast one proportional valve 513 and is configured to receive a firstworking fluid (e.g., hot gas such as exhaust gas) from a source (e.g.,an engine). The at least one proportional valve 513 is configured tocontrollably allow a first fraction of the first working fluid to flowin thermal communication with the at least one thermoelectric subsystem509 and to controllably allow a second fraction of the first workingfluid to flow through the at least one bypass conduit 511 such that thesecond fraction is not in thermal communication with the at least onethermoelectric subsystem 509. For example, the at least one proportionalvalve 513 can be integrated into the TEG system 500, the at least onebypass conduit 511 can be integrated into a main shell 515 of the TEGsystem 500, and the TEG system 500 can have double-wall thermalinsulation 517 (e.g., top and bottom walls) that provide thermalinsulation of the at least one thermoelectric subsystem 509 from theenvironment.

FIG. 14 schematically illustrates at least some external features of anexample TEG system 500 in accordance with certain embodiments describedherein. The TEG system 500 can comprise a TEG main shell 515, one ormore inlets 503 configured to receive the first working fluid (e.g.,exhaust gas), and one or more outlets 505 configured to output the firstworking fluid. The TEG system 500 can further comprise a coolingsubsystem 507 (e.g., coolant circuit) configured to receive a secondworking fluid (e.g., coolant, water) that flows in thermal communicationwith the at least one thermoelectric subsystem 509. For example, thecooling subsystem 507 can comprise one or more coolant conduits 519configured to receive and output the second working fluid and one ormore coolant manifolds 521 (e.g., one on each side of the TEG system500) configured to distribute the second working fluid to and from theat least one thermoelectric subsystem 509. The TEG system 500 canfurther comprise at least one valve actuator 523 in mechanicalcommunication with the at least one proportional valve 513 andconfigured to control the at least one proportional valve 513. Incertain embodiments, the TEG system 500 can include some or all of thestructures described above with regard to FIGS. 1-11.

FIGS. 15A and 15B schematically illustrate at least some internalfeatures of an example TEG system 500 in accordance with certainembodiments described herein. The TEG system 500 can comprise a doublewall thermal insulation structure 517 that is configured to at leastpartially thermally isolate the at least thermoelectric subsystem 509(e.g., at least one thermoelectric assembly 10) from the surroundingenvironment, from the at least one bypass conduit 511, or both. Theregion between the two walls of the double-wall thermal insulationstructure can contain a generally thermally insulative material.

FIGS. 16A-16C schematically illustrate the at least one proportionalvalve 513 in three different positions in accordance with certainembodiments described herein. The at least one proportional valve 513can comprise one or more movable structures (e.g., flap or flaps)configured to vary the entrance area of the at least one bypass conduit511 through which the first working fluid can flow and to vary theentrance area of the thermoelectric subsystem 509 through which thefirst working fluid can flow. For example, the at least one proportionalvalve 513 can be controlled to vary the first fraction of the workingfluid to be any value between zero and 100% of the received workingfluid (e.g., 0%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%,80%, 85%, 90%, 95%, 100%). The at least one proportional valve 513 canbe controlled to vary the second fraction of the working fluid to be anyvalue between zero and 100% of the received working fluid (e.g., 0%, 5%,10%, 15%, 20%, 25%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%,100%). In certain embodiments having a single bypass conduit 511 and aplurality of thermoelectric subsystems 509 (e.g., as shown in FIGS. 14,15A, and 15B), the at least one proportional valve 513 (e.g., a singleproportional valve) can be configured to direct a first portion of thefirst working fluid through the bypass conduit 511 and the remainingportion of the first working fluid through the thermoelectric subsystems509. FIG. 16A illustrates the at least one proportional valve 513 in aposition that controls the flow such that 100% of the flow (indicated byarrows 525) is through the thermoelectric subsystem 509. FIG. 16Billustrates the at least one proportional valve 513 in a position thatcontrols the flow such that a fraction of the flow is through thethermoelectric subsystem 509 and the remaining fraction is through thebypass conduit 511. FIG. 16C illustrates the at least one proportionalvalve 513 in a position that controls the flow such that 100% of theflow is through the bypass conduit 511.

As discussed in accordance with other embodiments above, the at leastone thermoelectric subsystem 509 can comprise at least one“cartridge-based thermoelectric system” or “cartridge” with at least onethermoelectric assembly or at least one thermoelectric system asdisclosed in U.S. Pat. Appl. Publ. No. 2013/0104953 which isincorporated in its entirety by reference herein. The thermoelectricsubsystem 509 can be configured to apply a temperature differentialacross an array of thermoelectric elements of the thermoelectricsubsystem 509 in accordance with certain embodiments described herein.For example, FIG. 6B of U.S. Pat. Appl. Publ. No. 2013/0104953illustrates a perspective cross-sectional view of an example cartridgeof the thermoelectric subsystem 509 compatible with certain embodimentsdescribed herein. The cartridge of this figure can include an anodizedaluminum “cold side” tube which is in thermal communication with aplurality of thermoelectric elements, and a plurality of “hot side” heattransfer assemblies in thermal communication with the plurality ofthermoelectric elements, such that a temperature differential is appliedacross the thermoelectric elements. As described in U.S. Pat. Appl.Publ. No. 2013/0104953 regarding certain configurations, the “cold side”tube can have a first working fluid (e.g., water) flowing through it,and the “hot side” heat transfer assemblies can have a second workingfluid (e.g., gas or vapor) flowing across the “hot side” heat transferassemblies. The at least one proportional valve 513 can be used in a TEGsystem 100 that also includes one or more of the structures describedabove with regard to FIGS. 1-11.

Discussion of the various embodiments herein has generally followed theembodiments schematically illustrated in the figures. However, it iscontemplated that the particular features, structures, orcharacteristics of any embodiments discussed herein may be combined inany suitable manner in one or more separate embodiments not expresslyillustrated or described. In many cases, structures that are describedor illustrated as unitary or contiguous can be separated while stillperforming the function(s) of the unitary structure. In many instances,structures that are described or illustrated as separate can be joinedor combined while still performing the function(s) of the separatedstructures.

Various embodiments have been described above. Although the inventionshave been described with reference to these specific embodiments, thedescriptions are intended to be illustrative and are not intended to belimiting. Various modifications and applications may occur to thoseskilled in the art without departing from the spirit and scope of theinventions as defined in the appended claims.

What is claimed is:
 1. A thermoelectric power generating systemcomprising: at least one thermoelectric assembly comprising: at leastone first heat exchanger in thermal communication with at least a firstportion of a first working fluid, the first portion of the first workingfluid flowing through the at least one thermoelectric assembly; aplurality of thermoelectric elements in thermal communication with theat least one first heat exchanger; and at least one second heatexchanger in thermal communication with the plurality of thermoelectricelements and with a second working fluid flowing through the at leastone thermoelectric assembly, the second working fluid cooler than thefirst working fluid; and at least one heat exchanger portion configuredto have at least some of the first portion of the first working fluidflow through the at least one heat exchanger portion after having flowedthrough the at least one thermoelectric assembly, the at least one heatexchanger portion configured to recover heat from the at least some ofthe first portion of the first working fluid.